Gain / Loss percentage is wrongly calculated

Hi, from what values is percentage calculated? I can’t get same numbers with simple calculation…

Examples without FX impact:

Avg price: 2980
Sell price: 3194.98
Gain/loss (app): 6.76%
Correct value: 7.21%

Avg price: 10.25
Sell price: 27.74
Gain/loss (app): 161.48%
Correct value: 170.63%

Avg price: 45.62
Sell price: 53.98
Gain/loss (app): 17.90%
Correct value: 18.32%


It is difficult to help without more information. In what type of account is this? What are the currencies?


It should not depends on currency. That’s why you have FX impact calculation on top of it.

If you buy stock at 10 usd and current sell price is 20 usd, gain should be 100%, not e.g. 91.2%

Are your positions small ones? I recall that because of the way average purchase price is calculated and some rounding that takes place, the figures that are displayed for gain are inaccurate when small sums of money are involved. There was a post about this in the past. It would take an AI engine better than my brain to find it again.

Best thing to do if you want to know gain is to calculate it from your total investment cost and its value if sold today.

Every single calculation is wrong. With 1 share or with 200 shares, every bought at same time, at same price. But is stll simple math…

I checked the calculations in my ISA account.
All 100% correct.
I’m on Android app.

Ok, I suppose your account is in USD, GBP or EUR. Mine is in CZK, so it depends on currency. Still strange, even with some rounding errors, there should not be such huge difference.

I am on Android too.

Hang on a sec your account is in Czech Koruna? So you’ll always be facing the FX issue buying into pound/dollar/euro etc

The overall return is (gains/loss + FX impact)

If you go into any of the stocks on the app you should see a Return with a down arrow to see how it’s split.

If you work out the maths you need to take the exchange rate at the time of buying and the curent exchange rate back into CZK.

I am talking about calculation WITHOUT fx impact all the time = gain/loss. In your case is correct (1.3302%)

1 Like

Yeah so buying that US share cost me £363.17 in pounds, based on the current SP and exchange it’s now worth £368.75

363.17 + 4.84 from bid increase + 0.74 from the dollar getting stronger = £368.75

Can you do a screengrab of one of yours which isn’t correct?

But the gain / loss value should be always calculated with the exchange rate you bought the stock. Then you will get gain at the same percentage in any currency. And of top of it you calculate the diff between current fx rate (fx impact).

The gain/loss RETURN is calculated totally in your home currency. Cost is cost in home currency at time you bought using exchange rate then. Value is value in home currency right now using exchange rate now.

RETURN % = (Value-Cost)/Cost x 100%
GAIN/LOSS % = price change % in other currency
FX IMPACT % = difference between the two above.

491.32-484.87= 6.45 dollar increase

$6.45 in pounds this second is £4.84

Gain should be 49.90%, cca 7 485 CZK

64.25-42.86 = 21.39 dollars

(15.649806*21.39) = 334.74935 dollars

334.74935 dollars in czk is the ~7,303.04

But you calculating with current fx rate.

1 stock, 10USD, 23CZK/USD, Total value 230 CZK

Current sell price 20 USD.

Gain should be 100%, 230 CZK, Total value 460 CZK

FX rate is now 22CZK/USD (-4.34%, 19.96CZK)

Total value 440.036 CZK

So from what I see the gain/loss amount is 100% correct.
But the gain/loss % is slightly out.
I guess the gain/loss % calculation needs to be done in USD only rather then whatever is causing the small discrepancy.
64.25/42.86 = 1.499 so 49.9% is the correct gain/loss %.

And the calculation for the correct gain/loss amount is what Phil showed.
64.25-42.86 = 21.39 dollars
(15.649806*21.39) = 334.74935 dollars
334.74935 dollars in czk is the ~7,303.04 which is what the app shows.

Anyway it just a small cosmetic issue and doesn’t impact you financially in any way.
I’m sure T212 can out it on their list as something to look into.

The stock was bought at 22.36 rate.

Gain should be 22.36 x 334.74935 = 7485 CZK (49.9%)

The overall calculation is correct, but more shares you have and more expensive, the diff is bigger and it is very misleading. 10% is huge difference :wink: ,

This text from a previous post may help. Let

AD = average USD price per share
AG = average GBP price per share
CD = current USD sell price per share
FX = current GBP per USD


RETURN% = (CD * FX/AG - 1) * 100%
FX IMPACT% = (AD * FX/AG - 1) * 100%

Note that this is not the true GAIN/LOSS% that would be experienced by a USD investor. The value that a US investor would look at is simply (CD/AD-1)*100%. What we have above is USD gain/loss per share, converted at today’s exchange rate to GBP, and then expressed as a percentage of the average GBP cost per share ie (CD-AD)*FX/AG * 100%

In truth RETURN should be [GAIN/LOSS] x [FX IMPACT] since these effects are actually multiplicative not additive. But it is easier to understand if we make them additive, which is what is done with the definition of GAIN/LOSS% as the difference of the other two,

The approximation being used here is

(1+a)(1+b) = 1 + a + b + ab, and imagine ab is small.

A gain of +1% combined with fx effect of +2% is actually (1.01)(1.02) = 1.0302 ie 3.01%. But it is clearer to most people if this is shown additive.